U.S. patent application number 13/061630 was filed with the patent office on 2011-06-23 for device for generating codebook, method for generating codebook, and method for transmitting data.
Invention is credited to Chung Gu Kang, Ji Hyung Kim, Jin-Woo Kim, ByungSeung Kwon, DongSeung Kwon, Wooram Shin, Young Seog Song, Choongil Yeh.
Application Number | 20110150129 13/061630 |
Document ID | / |
Family ID | 42178213 |
Filed Date | 2011-06-23 |
United States Patent
Application |
20110150129 |
Kind Code |
A1 |
Kwon; DongSeung ; et
al. |
June 23, 2011 |
DEVICE FOR GENERATING CODEBOOK, METHOD FOR GENERATING CODEBOOK, AND
METHOD FOR TRANSMITTING DATA
Abstract
A device for generating a transmission codebook in a
communication system including a multi-input multi-output (MIMO)
antenna according to an embodiment of the present invention
includes: a frequency determiner that determines a frequency to
allow the transmission codebook to have an optimal characteristic;
a precoding matrix generator that generates a precoding matrix on
the basis of the frequency; and a codebook generator that generates
a retransmission codebook to be used for retransmission on the
basis of the precoding matrix and generates the transmission
codebook on the basis of the retransmission codebook.
Inventors: |
Kwon; DongSeung; (Daejeon,
KR) ; Kwon; ByungSeung; (Seoul, KR) ; Yeh;
Choongil; (Daejeon, KR) ; Song; Young Seog;
(Daejeon, KR) ; Kim; Ji Hyung; (Daejeon, KR)
; Shin; Wooram; (Daejeon, KR) ; Kang; Chung
Gu; (Seoul, KR) ; Kim; Jin-Woo; (Seoul,
KR) |
Family ID: |
42178213 |
Appl. No.: |
13/061630 |
Filed: |
September 1, 2009 |
PCT Filed: |
September 1, 2009 |
PCT NO: |
PCT/KR09/04899 |
371 Date: |
March 1, 2011 |
Current U.S.
Class: |
375/295 |
Current CPC
Class: |
H04B 7/0639 20130101;
H04L 1/1812 20130101; H04B 7/0652 20130101; H04L 1/06 20130101 |
Class at
Publication: |
375/295 |
International
Class: |
H04L 27/00 20060101
H04L027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2008 |
KR |
10-2008-0085927 |
Aug 4, 2009 |
KR |
10-2009-0071799 |
Claims
1. A device for generating a transmission codebook in a
communication system including a multi-input multi-output (MIMO)
antenna, comprising: a frequency determiner that determines a
frequency to allow the transmission codebook to have an optimal
characteristic; a precoding matrix generator that generates a
precoding matrix on the basis of the frequency; and a codebook
generator that generates a retransmission codebook to be used for
retransmission on the basis of the precoding matrix and generates
the transmission codebook on the basis of the retransmission
codebook.
2. The device of claim 1, wherein the transmission codebook has the
optimal characteristic when a minimum distance of the transmission
codebook becomes a maximum.
3. The device of claim 1, further comprising a storage unit that
stores an initial codebook used for initial transmission.
4. The device of claim 3, wherein the transmission codebook is
generated by concatenating the initial codebook and the
retransmission codebook.
5. The device of claim 1, wherein the precoding matrix is an
orthogonal matrix using an exponential function of a value found by
dividing the frequency by the size of the transmission codebook as
an element.
6. The device of claim 5, wherein the retransmission codebook is
generated by multiplying the precoding matrix by a unitary
matrix.
7. The device of claim 1, wherein the frequency is a frequency for
maximally preventing an error of a signal received by a reception
device of the communication system from being generated.
8. A method for generating a transmission codebook in a device for
generating a codebook in a communication system including a
multi-input multi-output (MIMO) antenna, comprising: determining a
frequency to allow the transmission codebook to have an optimal
characteristic; generating a precoding matrix on the basis of the
optimal frequency; generating a retransmission codebook to be used
for retransmission on the basis of the precoding matrix; and
generating the transmission codebook on the basis of the
retransmission codebook.
9. The method of claim 8, wherein the transmission codebook has the
optimal characteristic when a minimum distance of the transmission
codebook becomes a maximum.
10. The method of claim 8, further comprising storing an initial
codebook used for initial transmission.
11. The method of claim 10, wherein generating the transmission
codebook includes concatenating the initial codebook and the
retransmission codebook.
12. The method of claim 10, wherein the precoding matrix is an
orthogonal matrix using an exponential function of a value found by
dividing the frequency by the size of the transmission codebook as
an element.
13. The method of claim 12, wherein generating the retransmission
codebook includes generating the retransmission codebook by
multiplying the precoding matrix by a unitary matrix.
14. A method for transmitting data in a transmission device of a
communication system including a multi-input multi-output (MINO)
antenna, comprising: multiplying a first precoding matrix by a
transmission signal vector corresponding to the data and
transmitting the multiplied transmission signal vector and first
precoding matrix; receiving a retransmission request from a
reception device; and multiplying a second precoding matrix by the
transmission signal vector and transmitting the multiplied
transmission signal vector and second precoding matrix, wherein the
second precoding matrix is selected in a transmission codebook
consisting of an initial codebook selected by the first precoding
matrix and a retransmission codebook determined by considering the
initial codebook.
15. The method of claim 14, wherein the second precoding matrix is
generated on the basis of a frequency value so that a minimum
distance of the transmission codebook becomes a maximum.
16. The method of claim 15, wherein the second precoding matrix is
an orthogonal matrix using an exponential function of a value found
by dividing the frequency by the size of the transmission codebook
as an element.
17. The method of claim 15, wherein the frequency is a frequency
for maximally preventing an error of a signal received by a
reception device of the communication system from being
generated.
18. The method of claim 14, wherein the transmission codebook is
generated by concatenating the initial codebook and the
retransmission codebook.
19. The method of claim 14, wherein the retransmission codebook is
generated by multiplying the second precoding matrix by a unitary
matrix.
20. The method of claim 14, wherein the second precoding matrix is
received from the reception device.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. Section
371, of PCT International Application No. PCT/KR2009/004899, filed
Sep. 1, 2009, which claimed priority to Korean Application No.
10-2008-0085927, filed Sep. 1, 2008 and Korean Application No.
10-2009-0071799, filed Aug. 4, 2009, the disclosures of which are
hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a device for generating a
codebook, a method for generating a codebook, and a method for
transmitting data.
BACKGROUND ART
[0003] As wireless communication systems are being developed, the
demand for improving speed thereof is increasing. In order to meet
the demand, a wide frequency band needs to be used, but frequency
resources are limited. As a result, as a method of transmitting
more data while using the limited frequency band, a multi-input
multi-output (MIMO) antenna technology is being used.
[0004] In the MIMO antenna technology, a precoding matrix selected
in a codebook that is a set of a plurality of predetermined
precoding matrices and a transmission signal vector are multiplexed
and transmitted to a plurality of antennas. At this time, a
receiving device selects a precoding matrix in the codebook on the
basis of information on a state of a channel, and feeds back the
selected precoding matrix to a transmitting device.
[0005] Meanwhile, a retransmission scheme of the wireless
communication system includes a retransmission scheme in a medium
access control (MAC) layer and a hybrid automatic retransmit
request (HARQ) scheme integrating and using link performance of a
physical layer. The HARQ scheme is a technology for recovering
received data by combining retransmitted data with received
information of previously transmitted data. In the HARQ scheme, the
receiving device determines whether or not an error is generated in
the reception signal by using, for example, a cyclic redundancy
check (CRC) code. As the determination result, the receiving device
transmits an acknowledge (ACK) message when no error is generated
and transmits a negative acknowledge (NACK) message when an error
is generated.
[0006] In the MIMO antenna technology, in the case of utilizing the
codebook and adopting the HARQ, when the precoding matrix is
selected in retransmission due to an initial transmission error in
the same manner as the initial transmission, a diversity gain
caused by the retransmission cannot be fully acquired. When the
precoding matrix is selected in retransmission by utilizing
reception information of the initial transmission, an optimum
precoding matrix may be selected, but for this, information on the
precoding matrix should be transmitted from the receiving
device.
[0007] In order to maximize the retransmission diversity gain
without receiving additional precoding matrix information from the
receiving device, a set of the optimum precoding matrices needs to
be generated.
[0008] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention and therefore it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
DISCLOSURE OF INVENTION
Technical Problem
[0009] The present invention has been made in an effort to create a
codebook capable of securing optimum transmission efficiency at the
time of retransmitting a signal vector due to a failure in initial
transmission in a multi-input multi-output (MIMO) antenna
technology.
Solution to Problem
[0010] An exemplary embodiment of the present invention provides a
device for generating a transmission codebook in a communication
system including a multi-input multi-output (MIMO) antenna, that
includes: a frequency determiner that determines a frequency to
allow the transmission codebook to have an optimal characteristic;
a precoding matrix generator that generates a precoding matrix on
the basis of the frequency; and a codebook generator that generates
a retransmission codebook to be used for retransmission on the
basis of the precoding matrix and generates the transmission
codebook on the basis of the retransmission codebook.
[0011] The device may further include a storage unit that stores an
initial codebook used for initial transmission.
[0012] The transmission codebook may be generated by concatenating
the initial codebook and the retransmission codebook.
[0013] The precoding matrix may be an orthogonal matrix using an
exponential function of a value found by dividing the frequency by
the size of the transmission codebook as an element.
[0014] The retransmission codebook may be generated by multiplying
the precoding matrix by a unitary matrix.
[0015] The frequency may be a frequency for maximally preventing an
error of a signal received by a reception device of the
communication system from being generated.
[0016] Another embodiment of the present invention provides a
method for generating a transmission codebook in a device for
generating a codebook in a communication system, that includes:
determining a frequency to allow the transmission codebook to have
an optimal characteristic; generating a precoding matrix on the
basis of the optimal frequency; generating a retransmission
codebook to be used for retransmission on the basis of the
precoding matrix; and generating the transmission codebook on the
basis of the retransmission codebook.
[0017] The method may further include storing an initial codebook
used for initial transmission.
[0018] Generating the transmission codebook may include
concatenating the initial codebook and the retransmission
codebook.
[0019] The precoding matrix may be an orthogonal matrix using an
exponential function of a value found by dividing the frequency by
the size of the transmission codebook as an element.
[0020] Generating the retransmission codebook may include
generating the retransmission codebook by multiplying the precoding
matrix by a unitary matrix.
[0021] Yet another embodiment of the present invention provides a
method for transmitting data in a transmission device of a
communication system including a multi-input multi-output (MINO)
antenna, that includes: multiplying a first precoding matrix by a
transmission signal vector corresponding to the data and
transmitting the multiplied transmission signal vector and first
precoding matrix; receiving a retransmission request from a
reception device; and multiplying a second precoding matrix by the
transmission signal vector and transmitting the multiplied
transmission signal vector and second precoding matrix, wherein the
second precoding matrix is selected in a transmission codebook
consisting of an initial codebook selected by the first precoding
matrix and a retransmission codebook determined by considering the
initial codebook.
[0022] The second precoding matrix may be generated on the basis of
a frequency value so that a minimum distance of the transmission
codebook becomes a maximum.
[0023] The second precoding matrix may be an orthogonal matrix
using an exponential function of a value found by dividing the
frequency by the size of the transmission codebook as an
element.
[0024] The frequency may be a frequency for maximally preventing an
error of a signal received by a reception device of the
communication system from being generated.
[0025] The transmission codebook may be generated by concatenating
the initial codebook and the retransmission codebook.
[0026] The retransmission codebook may be generated by multiplying
the second precoding matrix by a unitary matrix.
[0027] The second precoding matrix may be received from the
reception device.
Advantageous Effects of Invention
[0028] According to an embodiment of the present invention, in a
MIMO antenna technology, it is possible to secure transmission
efficiency by selecting an optimum precoding matrix at the time of
retransmitting a signal vector due to a failure in initial
transmission.
BRIEF DESCRIPTION OF DRAWINGS
[0029] FIG. 1 is a schematic block diagram of a device for
generating a codebook according to an embodiment of the present
invention;
[0030] FIG. 2 is a graph illustrating error rates according to a
signal to noise ratio (SNR) when a precoding matrix selected in a
codebook in the related art is adopted and when a precoding matrix
selected in a codebook according to an embodiment of the present
invention is adopted, in an environment without a spatial channel
correlation; and
[0031] FIG. 3 is a graph illustrating error rates according to a
signal to noise ratio (SNR) when a precoding matrix selected in a
codebook in the related art is adopted and when a precoding matrix
selected in a codebook according to an embodiment of the present
invention is adopted, in an environment with a spatial channel
correlation.
MODE FOR THE INVENTION
[0032] In the following detailed description, only certain
exemplary embodiments of the present invention have been shown and
described, simply by way of illustration. As those skilled in the
art would realize, the described embodiments may be modified in
various different ways, all without departing from the spirit or
scope of the present invention. Accordingly, the drawings and
description are to be regarded as illustrative in nature and not
restrictive. Like reference numerals designate like elements
throughout the specification.
[0033] In the specification, unless explicitly described to the
contrary, the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements.
[0034] In the specification, a terminal may designate a mobile
station (MS), a mobile terminal (MT), a subscriber station (SS), a
portable subscriber station (PSS), user equipment (UE), an access
terminal (AT), etc. and may include the entire or partial functions
of the terminal, the mobile terminal, the subscriber station, the
portable subscriber station, the user equipment, the access
terminal, etc.
[0035] In the specification, a base station (BS) may designate an
access point (AP), a radio access station (RAS), a node B, an
evolved node B (eNodeB), a base transceiver station (BTS), a mobile
multihop relay (MMR)-BS, etc., and may include the entire or
partial functions of the AP, the RAS, the node B, the eNodeB, the
BTS, the MMR-BS, etc.
[0036] Hereinafter, a device for generating a codebook and a method
for generating a code book according to an embodiment of the
present invention will be described in detail with reference to the
accompanying drawings.
[0037] In a wireless communication system according to an
embodiment of the present invention, a relationship between
transmission and reception signal vectors can be expressed as shown
in Equation 1.
y = [ y 1 y 2 y L ] = [ H 1 F 1 H 2 F 2 H L F L ] s + [ w 1 w 2 w L
] = H CONC s + w ( Equation 1 ) ##EQU00001##
[0038] Herein, H.sub.1, H.sub.2, . . . , H.sub.L represent channel
matrices in first, second, . . . , L-th transmissions, F.sub.1,
F.sub.2, . . . , F.sub.L represent precoding matrices in first,
second, L-th transmissions, w.sub.1, w.sub.2, represent thermal
noise vectors in first, second, . . . , L-th transmissions, s
represents a transmission signal vector, y represent reception
signal vectors transmitted in first, second, . . . , L-th
transmissions, and Hconc represents an effective channel
matrix.
[0039] Equation 1 can be expressed in a form in which the channel
matrices are block-diagonalized as shown in Equation 2.
y = [ H 1 F 1 H 2 F 2 H l F l ] s + [ w 1 w 2 w l ] = [ H 1 H 2 H l
] [ F 1 F 2 F l ] s + [ w 1 w 2 w l ] ( Equation 2 )
##EQU00002##
[0040] The precoding matrices F.sub.1, F.sub.2, . . . , F.sub.L
expressed above are selected in a predetermined codebook.
Therefore, a device for generating a codebook according to an
embodiment of the present invention will be described in
detail.
[0041] FIG. 1 is a schematic block diagram of a device for
generating a codebook according to an embodiment of the present
invention.
[0042] Referring to FIG. 1, the codebook generating device 100
includes a frequency determiner 110, a precoding matrix generator
120, a storage unit 130, and a codebook generator 140.
[0043] The frequency determiner 110 determines a frequency
u.sub.1,u.sub.2, . . . u.sub.N.sub.T
that allows the codebook generated in the codebook generator 100 to
have an optimal characteristic.
[0044] The precoding matrix generator 120 generates a precoding
matrix (I) by using the frequency determined by the frequency
determiner 110 and the size C of the codebook. The precoding matrix
(1) is expressed as shown in Equation 3.
.PHI. = diag { exp ( j 2 .pi. C u 1 ) exp ( j 2 .pi. C u 2 ) exp (
j 2 .pi. C u N T ) } ( Equation 3 ) ##EQU00003##
[0045] Herein, "diag" represents a diagonal matrix and "exp"
represents an exponential function. That is, the precoding matrix
.PHI. is a diagonal matrix using an exponential function of a value
found by dividing the size C of the codebook by the optimal
frequency
u.sub.1,u.sub.2, . . . , u.sub.N.sub.T
as an element.
[0046] The storage unit 130 stores a codebook (hereinafter referred
to as "initial codebook") (M.sub.i, i=1, 2, . . . , c) used in
initial transmission.
[0047] The codebook generator 140 receives the precoding matrix 1)
from the precoding matrix generator 120, and generates a
retransmission codebook (M.sub.i,2, i=1, 2, . . . , c) to be used
for retransmission on the basis of the received precoding matrix O.
The retransmission codebook M.sub.i,2 is expressed as shown in
Equation 4.
M.sub.i,2=.PHI..sup.i-1D (Equation 4)
[0048] In Equation 4, D represents a predetermined unitary matrix.
That is, the retransmission codebook M.sub.i,2 is generated by
multiplying the generated precoding matrix .PHI. by the
predetermined unitary matrix.
[0049] The codebook generator 140 generates a transmission codebook
U; (i==1, 2, . . . , c) by using the initial codebook M; and the
retransmission codebook M.sub.i,2 from the storage unit 130. The
transmission codebook U, is expressed as shown in Equation 5.
{ U 1 = [ M 1 M 1 , 2 ] , U 2 = [ M 2 M 2 , 2 ] , , U C = [ M C M C
, 2 ] } ( Equation 5 ) ##EQU00004##
[0050] Referring to Equation 5, the transmission codebook U, is
generated in a form in which the initial codebook M.sub.i and the
retransmission codebook M.sub.i,2 are concatenated with each other.
A reception device (not shown) selects the retransmission codebook
M.sub.i,2 to be used for retransmission in accordance with the
initial codebook M.sub.i used for the initial transmission in
accordance with the transmission codebook U.sub.i, and selects the
precoding matrix in accordance with the retransmission codebook
M.sub.i,2.
[0051] Meanwhile, the frequency determiner 110 determines the
frequency
u.sub.1,u.sub.2, . . . u.sub.N.sub.T
that allows the transmission codebook U; generated in the codebook
generator 140 to have an optimal characteristic at the time of
determining the frequency
u.sub.1,u.sub.2, . . . u.sub.N.sub.T
That is, the optimal frequency
u.sub.1,u.sub.2, . . . u.sub.N.sub.T
is the frequency
u.sub.1,u.sub.2, . . . u.sub.N.sub.T
for maximally preventing an error of the reception signal in the
reception device from being generated.
[0052] Herein, the optimal frequency
u.sub.1,u.sub.2, . . . u.sub.N.sub.T
is determined to maximize a minimum distance d.sub.min of the
transmission codebook U.sub.i generated in the codebook generator
140. The minimum distance is expressed as shown in Equation 6.
d min = min p , q p .noteq. q U p U p H - U q U q H 2 ( Equation 6
) ##EQU00005##
[0053] Hereinafter, referring to FIGS. 2 and 3, performance
improvement when the precoding matrix generated in the codebook
generating device according to the embodiment of the present
invention is adopted will be described in detail.
[0054] FIG. 2 is a graph illustrating error rates according to a
signal to noise ratio (SNR) when a precoding matrix selected in a
codebook in the related art is adopted and when a precoding matrix
selected in a codebook according to an embodiment of the present
invention is adopted, in an environment without a spatial channel
correlation.
[0055] Referring to FIG. 2, error rates according to the SNR are
illustrated when the precoding matrix selected in the code book in
the related art is adopted in the case when a channel is not
changed (a), when the precoding matrix selected in the codebook
according to an embodiment of the present invention is adopted in
the case when the channel is not changed (b), when the precoding
matrix selected in the codebook in the related art is adopted in a
channel environment in which a terminal moves at the speed of 3
km/h (c), and when the precoding matrix selected in the codebook
according to an embodiment of the present invention is adopted in
the channel environment in which the terminal moves at the speed of
3 km/h (d).
[0056] In both the case in which the channel is not changed and the
case in which the channel is changed, the case when the precoding
matrix selected in the codebook according to the embodiment of the
present invention is adopted has a lower error rate than the case
when the precoding matrix selected in the codebook in the related
art is adopted in the same SNR.
[0057] FIG. 3 is a graph illustrating error rates according to a
signal to noise ratio (SNR) when a preceding matrix selected in a
codebook in the related art is adopted and when a precoding matrix
selected in a codebook according to an embodiment of the present
invention is adopted, in an environment with a spatial channel
correlation.
[0058] Referring to FIG. 3, error rates according to the SNR are
illustrated when the precoding matrix selected in the related art
is adopted in the case when a channel is not changed (e), when the
precoding matrix selected in the codebook according to an
embodiment of the present invention is adopted in the case when the
channel is not changed (f), when the precoding matrix selected in
the codebook in the related art is adopted in a channel environment
in which a terminal moves at the speed of 3 km/h (g), and when the
preceding matrix selected in the codebook according to an
embodiment of the present invention is adopted in the channel
environment in which the terminal moves at the speed of 3 km/h
(h).
[0059] In both the case in which the channel is not changed and the
case in which the channel is changed, the case when the precoding
matrix selected in the codebook according to the embodiment of the
present invention is adopted has a lower error rate than the case
when the precoding matrix selected in the codebook in the related
art is adopted in the same SNR.
[0060] The above-mentioned exemplary embodiments of the present
invention are not embodied only by an apparatus and method.
Alternatively, the above-mentioned exemplary embodiments may be
embodied by a program performing functions that correspond to the
configuration of the exemplary embodiments of the present
invention, or a recording medium on which the program is
recorded.
[0061] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
* * * * *